For computer communication using optical networking, an optical fiber network includes an Optical Line Terminal (OLT) device, which is a terminating device of a carrier, and an Optical Network Terminal (ONT) device (also called an Optical Network Unit (ONU)), which is a terminating device of an end-user (a telecommunication subscriber). A splitting device called a star coupler is installed in the optical fiber network. The star coupler distributes light from a single input to multiple outputs. A single optical fiber of the OLT is branched and connected to a plurality of ONTs. Such a communication system is called a Passive Optical Network (PON). The PON is also called a Passive Double Star (PDS).
In the conventional technology of communication systems that include a terminating device, there is a disclosed communication device that recognizes, by using the header section of a received packet, that the packet is not received via a communication from a different communication device and recognizes that the packet contains a control signal for turning on/off the power source of the communication device so as to recognize the details of control to be performed on the communication device by using the control signal.
In another conventional technology, there is a disclosed communication system in which frame packet signals that each include a packet overhead section and frame synchronization information for establishing frame synchronization corresponding to the transmission speeds of slave communication devices are located within a single packet signal length or within a single packet time period in a divided manner and the frame packet signals are transmitted from a master communication device to the slave communication devices in a frame period interval.
In this conventional technology, the slave communication device receives, from the frame packet signals that are divided within a single packet signal length or within a single packet time period, a frame packet signal that conforms to the transmission speed of the slave communication device and reads the frame synchronization information so as to establish frame synchronization.
Patent Document 1: Japanese Laid-open Patent Publication No. 09-064894
Patent Document 2: Japanese Laid-open Patent Publication No. 2000-165368
In a communication network that includes a communication device as a terminating device, the communication device usually needs to have the power source turned on all the time so as to stand by for communication even when the communication device is in an idling state where communication is not performed. A master communication device, such as the above-described OLT, consumes a large amount of power because the master communication device has to perform communication with a plurality of slave communication devices, such as the above-described ONTs, in synchronization.
In terms of saving of energy, the problem is how to reduce the power consumption while the master communication device is in operation. Because the above-described conventional technologies are not designed from the perspective of saving energy, it is difficult to reduce the power consumption of the communication device.